Shutoff Switch Circuit Is Shorting Out Engine

[bobgritz]

My 1998 25HP Johnson is shorting out when the Push Button switch wires are attached. When the ground side is detached the engine runs but as soon as the switch is grounded the engine dies. I detached both wires from the switch and it tested okay (no elec flow when out, positive flow when depressed). My thinking is that there is a short in the power pack and wonder if this is a common problem?

 

[F_R]

I'd say the switch is bad. I'm not sure about the 1998, but at least on older motors there is a high voltage in the kill wire that is arcing across a defect in the switch that doesn't show up during low voltage testing. Power pack OK or it wouldn't be running.

 

[bobgritz]

Good suggestion. Perhaps I should simply cut the wires at the switch as a further test? If your theory proves correct, perhaps I could just attach a generic (but suitable) switch to the severed wires until I can locate a proper replacement??

 

[Vic.S]

Good suggestion. Perhaps I should simply cut the wires at the switch as a further test? If your theory proves correct, perhaps I could just attach a generic (but suitable) switch to the severed wires until I can locate a proper replacement??

I assume the stop button is also a safety kill switch with a lanyard. Is the lanyard clipped on to the button ?

 

[bobgritz]

Thank you Vic ... yes, it is the 'lanyard' type of kill switch and yes, it is inserted as it should be. The switch is working properly when tested with a simple 12 volt test light (lanyard-clip attached=open circuit vs. button depressed (or clip removed)=circuit closed). F_R mentioned that the switch may test properly with low voltage yet my test isn't necessarily valid due to a higher amount of continuous flow through the circuitry. Rather than purchase a new power pack, it seems that the simplest way to confirm a switch failure would be to clip it's wires. I'll give the forum a few more hours to talk me out of this procedure otherwise the switch goes under the knife! Thank you.

 

[Crosbyman]

Continuity wise ....your conclusion indicates a good working switch tested at 12 volts... yet d?fective under operating conditions.


​If that switch body is metal.... have you tested for continuity between the wires and.... the switch body itself either in stand alone mode or while pushing the kill button

​ one of those two wires may be grounding out to the switch's frame itself & killing the engine:laser:

same ending.... bad switch :sad:

 

[bobgritz]

SOLVED ... and, thank you.

I severed the wires to the switch and bingo ... it's alive ... it's alive ... the motor continued to run. When I touched the two 'severed' wires together, more bingo ... the engine shut off. These switches are sealed units and not likely worth the energy (or time) trying to repair so next step is finding a replacement. Thanks to all for showing me the forest for the trees! Or would that be the other way around, hmmm. Thanks and take care.

FWIW ... I acquired this engine in unknown and in as-is condition and have managed to iron out most of the wrinkles. It does have a periodic 'coughing' problem and as soon as I take a short video I'll post it for further expert review. If you want a preview here's the issue: it'll run well but about every 10 or 15 seconds it coughs and the entire outboard shutters for a moment ... then it's fine ... then a cough ... etc. It's usable as-is but it feels fixable. Perhaps this sounds familiar to someone out there ... btw, plugs are new.

 

[F_R]

When does the coughing occur? If at idle speed, it probably is a "lean sneeze", caused by running too lean. If while under way at significant speed, it probably is a worn out clutch dog in the lower unit. It is coming out of gear, rotating half a revolution, and slamming back into gear--till next time. Most people describe it as feeling like they struck an underwater object. Very common.